Juliette’s Plant Scherer remains the largest single emitter of greenhouse gases in the United States, data released Thursday from the U.S. Environmental Protection Agency shows.

The four coal-fired generating units together generated an estimated 21.8 million metric tons of greenhouse gas emissions last year. Nearly all of that came from carbon dioxide emissions, though the plant also released methane and nitrous oxides equivalent to about 165,000 metric tons of carbon dioxide.

Total emissions of greenhouse gases were down about 1 percent from the previous year.

Mark Williams, a spokesman for Georgia Power, said the plant’s large electrical generating capacity is the reason it generates so much carbon dioxide.

“We learned that yet again, Georgia is quite literally ground zero for the greenhouse gas emissions that are causing climate change around the world,” Gunning said.

Gunning and Williams agreed there is no proven way to reduce carbon dioxide emissions from coal plants. Carbon dioxide is released when fossil fuels, like coal, are burned. As more coal is burned to generate additional electricity, more carbon dioxide gets released.

Greenhouse gases act like a blanket to hold heat in the Earth’s atmosphere. A United Nations report released last month said scientists are 95 percent certain that people are causing most of the global warming.

Gunning said Georgia would benefit by replacing coal-fired plants with solar generation, by using power from wind turbines in wind-rich places like Oklahoma, or by improving energy efficiency.

“There are far cleaner, cheaper ways to produce electricity now that we should be ramping up,” Gunning said.

Williams said Georgia Power has invested about $2.5 billion into emissions controls at Plant Scherer since 2005. That equipment is fully installed on three of Scherer’s four generating units, and work on the other one will be complete next year.

Williams said the plant, which began operations in 1982, will be used indefinitely.

“It’s an important component in our generating mix,” he said. “We believe in having a diverse generating mix. That includes coal, natural gas, nuclear, renewable. Plant Scherer is simply one of the more important generating plants that we have.”